[Federal Register Volume 85, Number 49 (Thursday, March 12, 2020)]
[Notices]
[Pages 14466-14467]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-05047]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration


Supersession of Vertical Datum for Surveying and Mapping 
Activities for the Island of Tutuila, American Samoa

AGENCY: The Office of the National Geodetic Survey (NGS), National 
Ocean Service (NOS), National Oceanic and

[[Page 14467]]

Atmospheric Administration (NOAA), Department of Commerce (DOC).

ACTION: Notice of vertical datum supersession within American Samoa.

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SUMMARY: This Notice announces a decision by the National Geodetic 
Survey (NGS) to supersede the American Samoa Vertical Datum of 2002 
(ASVD 02) and revert back to Local Tidal (LT) as the official civilian 
vertical datum for surveying and mapping activities for the island of 
Tutuila, American Samoa. As a member of the Federal Geographic Data 
Committee, NOAA is responsible for defining, maintaining and providing 
access to the National Spatial Reference System. Within NOAA, the 
National Geodetic Survey has the responsibility to accomplish this 
task. Due to geophysical activity, the ASVD 02 vertical datum is 
destroyed. To provide for vertical control, it is necessary to revert 
to heights based on a LT datum. To the extent it is legally allowable 
and feasible, all surveys performed or financed by the Federal agencies 
using or producing vertical height information will undertake an 
orderly transition to LT tied to the tide gauge at Pago Pago. 
Exceptions are for those with specific military related applications, 
which will use their own datum.

DATES: Effective date of this supersession is upon publication of this 
notice.

ADDRESSES: National Geodetic Survey, 1315 East-West Highway, Silver 
Spring, MD, 20910.

FOR FURTHER INFORMATION CONTACT: Dr. Daniel Roman, Chief Geodesist, 
National Geodetic Survey, by email at [email protected], phone at 
(240) 533-9673 or mail at NOAA/NOS/NGS 1315 East-West Highway, Silver 
Spring, MD, 20910.

SUPPLEMENTARY INFORMATION: The National Geodetic Survey (NGS), National 
Ocean Service (NOS), has determined that the bench marks providing 
geodetic control for ASVD 02 shifted as a result of movements from 
earthquakes. Additionally, the Primary Bench Mark (PBM) associated with 
ASVD 02 at the Pago Pago tide gauge (177 0000 S) was determined to be 
unstable and was later destroyed in 2015. Consequently, neither the 
leveled bench marks nor the datum point associated with ASVD 02 is 
suitable for geodetic control. The North American Pacific Vertical 
Datum of 2022 (NAPGD2022) will replace ASVD 02 in the next few years. 
Rather than develop an interim product between now and then, Local 
Tidal (LT) will be used until NAPGD2022 is implemented. This will 
necessitate, until 2022, the incorporation of the tide gauge at Pago 
Pago Harbor into surveys requiring vertical control.
    The basis for all LT heights is Mean Sea Level (MSL). The current 
National Tidal Datum Epoch (NTDE) is for the period 1983-2001. The Pago 
Pago tide gauge record was also disturbed by the earthquakes, and a 
provisional station datum was established from observations from 2011-
2016. The Pago Pago tide station, therefore, is not formally a part of 
the current NTDE, because it is not based on the specified 18.6 year 
tidal cycle. A Station Datum (SD) has been determined by the NOS Center 
for Operational Oceanographic Products and Services (CO-OPS), and 
published for the National Water Levels Observation Network (NWLON) 
bench mark number 177 0000 W (4.345 meters above the SD and 2.955 
meters above MSL for the 2011-2016 observation period), located in Pago 
Pago. This bench mark should be occupied to complete geodetic surveys 
on the island of Tutuila in American Samoa. If occupation of the 
primary tidal bench mark is not practicable, other tidal bench marks 
for Pago Pago may be occupied for geodetic control, but they must be 
listed on the CO-OPS bench mark sheet at the time of the survey 
(https://tidesandcurrents.noaa.gov/benchmarks.html?id=1770000). Note 
that no other islands of American Samoa are part of ASVD 02, and they 
remain on their own respective LT datum.
    Information for individual geodetic control monuments is available 
in digital form from the NGS website: https://geodesy.noaa.gov/datasheets/index.shtml. Information on Pago Pago tidal bench marks is 
available at https://tidesandcurrents.noaa.gov/benchmarks.html?id=1770000.

(Authority: Coast and Geodetic Survey Act of 1947, 33 U.S.C. 883a et 
seq.)


William B. Kearse,
Acting Director, National Geodetic Survey, National Ocean Service, 
National Oceanic and Atmospheric Administration.
[FR Doc. 2020-05047 Filed 3-11-20; 8:45 am]
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